Method for chemical vapor deposition of fitted surfaces in coupled article

ABSTRACT

A coupled article formed by having a pair of members inserted one into the other is placed within a plating chamber. The vapor of an extremely hard coating material is introduced into said chamber while a rotational or vibrational motion is conferred upon one of the pair of members, so that said coating material is deposited to a prescribed thickness on the fitted surfaces of the pair of members composing said coupled article.

United States Patent Okamoto 1 Aug. 19, 1975 METHOD FOR CHEMICAL VAPOR [56] References Cited DEPOSITION OF FITTED SURFACES IN UNITED STATES PATENTS COUPLED ARTICLE 2,130,879 9/1938 Dobke 117/1072 R x 5 Inventor: Shigetake Okamoto Tokyo Japan 2 88() 1 18 3/1959 Taylor 1 17/D1G. 8 36371320 1/1972 Wakefield et a1 117/106 C X [73] Assignee: Agency of Industrial Science &

gy, Y p n Primary E.\'aminerLeon D. Rosdol Assistant E.\'umir1erHarris A. Pitlick [22] Ffled 1973 Attorney, Agent, or Firm-Kurt Kelman [21} Appl. No.: 405,536 7 [57] ABSTRACT 30 Foreign Application Priority Data rs article i byhavling gp j inserte one into t e 0t er is ace wit in a atm OcL 11 1972 Japan 47401789 Chamben The vapor of an extrgmely hard comigg 5 [52] US- Cl 427/232; 117/106 C; 117/1072 R; terial is IIlII'OdUCCd into Saki chamber while a rota- HWDIG. 8; 29/445;427/235;427/237; tional or vibrational motion is conferre i upon one of 427/249; 427/346 the pair of members so that said coating material is 51 Int. Cl. C23c 11/00 deposted to Prescrbed h'ckness thefimd 58 1 Field of Search 117/106 R, 106 A, 106 C, faces of the members Composmg Coupled 117/1072 R, DIG. 8

article.

2 C1aims, 1 Drawing Figure METHOD FOR CHEMICAL VAPOR DEPOSITION OF FITTED SURFACES IN COUPLED ARTICLE BACKGROUND OF THE INVENTION This invention relates to a method for the chemical vapor deposition of fitted surfaces of a pair of members composing a coupled article. More particularly, this invention relates to a method for the chemical vapor deposition of an extremely hard coating material such as TiN or TiC on the fitted surfaces of a coupled article formed by having a pair of members inserted one into the other, such as a fuel pump or a high-speed precision roller bearing, for example.

By the chemical vapor deposition of an extremely hard coating material such as TiN or TiC on an iron or steel material, there are obtained materials which are low in price and high in abrasion-resistance.

When the fitted surfaces of a pair of members composing a coupled article are subjected to chemical vapor deposition of an extremely hard coating material, the layer of a coating material to be deposited on the fitted surfaces in such coupled article is required to be controlled accurately to a prescribed thickness since, the clearance allowed in precision coupled articles generally falls in the range of from 2 to microns. In order for the layer of coating material deposited on the fitted surfaces of a given article by a chemical vapor deposition method to be finished accurately to a prescribed thickness, the plating temperature, the flow volume of a carrier gas in use and the volume of the vapor of coating material must be regulated with high accuracy. Even if the plating operation is performed under rigid control of the factors mentioned above, the thickness of the deposited layer of the plating material is only accurate to within i 2 microns. When. the individual members which go to make up a desired coupled article are separately subjected to the chemical vapor deposition, the members which now have their surfaces coated are often found to be no longer capable of coupling. In this case, it becomes necessary to adopt an extra step for removing by abrasion the excess thickness of the layer of coating material deposited on the fitted surfaces so as to give the individual members required dimensions and surface roughness. This is extremely difficult to accomplish, however, because the abrasion of the deposited layer of the extremely hard coating material must resort to diamond lapping or some other treatment of that nature. When the pair of members for a desired coupled article are joined in a normally assembled form and then subjected to the chemical vapor deposition, the vapor of the coating material can disperse into even the smallest opening and deposit itself even on the fitted surfaces. This, consequently, renders it impossible to maintain the fitted surfaces accurately by a uniform clearance. According to this method, therefore, no uniform thickness is obtained in the deposited layer of the coating material. When the coating material is deposited excessively along the fitted surfaces, there is a possibility that the two members will be fastened to each other.

An object of this invention is to provide a method for the chemical vapor deposition of an extremely hard coating substance to a required thickness on fitted surfaces of a coupled article without requiring accurate control of such factors as plating temperature, flow volume of carrier gas and amount of the vapor of coating substance.

To accomplish the aforementioned object, the

method for the chemical vapor deposition of fitted sur-' faces of a coupled article according to the present invention, in carrying out said chemical vapor deposition, causeschemical vapor deposition of an extremely hard substance on said fitted surfaces while conferring a rotational o r vibrational motion on one of the pair of members composing said coupled article, with the pair of members maintained ina normally assembled form. When the chemical vapor deposition is carried out on the pair of members which are coupled by being inserted one in the other in a'normally assembled form, the extent to which the plating work has progressed can be found by observing the change in torque or frequency resulting from the progress of plating. Further, the plated surfaces are rubbed against each other because of the rotational or vibrational motion conferred on one of the members, so that the abrasion smoothens the surfaces and gives the fitted surfaces of the coupled article a prescribed thickness of plating layer.

Other objects and other characteristic features of this invention will becomeapparent from the description to be given in further detail herein below with reference to the accompanying drawing.

BRIEF EXPLANATION OF THE DRAWING The drawing attached hereto is a sectional view in side elevation of one preferred embodiment of the device for practicing the method of this invention.

DETAILED DESCRIPTION oF H INVENTION 1 and a barrel 2 is assembled in advance and, in that state, placed inside a plating chamber 3. Inside the plating chamber 3, the barrel 2 is fastened in position by a supporting arm 4 and the plunger 1 is held stably by a chuck 5 and connected, by the medium of a supporting arm 5, to a driving apparatus 6 such as of a motor or oscillator so as to be given a rotational or vibrational motion. To said supporting element 5 is attached a sensor 7 such as a torque meter or a vibration meter,

- which serves to measure and indicate torque or frequency from said driving apparatus 6. Torque or frequency may be detected by directly attaching this sensor to the driving apparatus. The top and the bottom of the plating chamber are provided with rubber seals 11 and 12 respectively so that the interior of the plating chamber will be maintained air-tight in spite of the motion from the driving apparatus. The outer wall of the plating chamber 3 is provided with a heating apparatus 10 such as a high-frequency coil which serves the purpose of maintaining the article to be plated at a prescribed temperature.

The members 1 and 2 subjected to plating are heated to a temperature between l,l00 l,20()C by means of the high-frequency coil 10. The driving apparatus 6 is set into operation to confer a rotational or vibrational motion upon the plunger 1. Simultaneously, a plating vapor prepared by mixing a carrier gas at a stated proportion with a vapor of metal compound salt reacted with said carrier gas to form an extremely hard substance with the aid ofa vaporizer (not illustrated) is fed into an inlet 8 of the plating chamber 3. Since the plating vapor has a characteristic property of penetrating into even the smallest opening, it can form a desposited layer not merely on exposed surfaces but on fitted surfaces of the members subjected to plating. The carrier gas which has fulfilled its part is discharged through an outlet 9.

ln carrying out the plating of this invention while keeping the plunger in a rotational motion, the suitable peripheral speed of the plunger falls in the range of from l,000 to 3,000 m/min. When the plating is given while the plunger is kept in a vibrational motion, it is suitable to select the stroke of vibration in the range of from to 10 mm and the frequency in the range of from 2,000 to 6,000 vibrations per second. These ranges are given solely by way of example and, therefore, they are naturally variable with the size of the plunger, the roughness of the plated surfaces, the size of clearance, etc. These ranges may suitably be moified when the plating is given to roller bearings.

As a deposited layer of the vaporized coating material begins to form on the fitted surfaces, the clearance intervening between the opposed surfaces is gradually decreased, with the result that a proportional change is brought about in the torque or frequency of vibrations. Measurement of this change by the sensor 7 enables one to tell accurately the extent of progress of the plating work. When this change has reached a prescribed level, the plating operation can be terminated by discontinuing the operation of the driving apparatus.

Metal compound salt such as titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, Wolfram hexachloride, molybdenum hexachloride, silicon chloride, boron chloride, etc. heretofore known to the art may be used as a vapor source reacted with a carrier gas to form an extremely hard coating material. As a carrier gas, nitrogen, hydrogen, oxygen, methane, etc. can be used.

The mixing ratio of the vapor from the vapor source to carrier gas may suitably be adjusted according to conventional chemical vapor deposition methods. Hydrocarbon may be added to the plating vapor as an additive, if necessary.

Since the chemical vapor deposition by this invention is carried out as the surfaces subjected to plating are slid over each other, the coating material is always deposited to a uniform thickness without calling for accurate control of plating temperature, flow volume of carrier gas, volume of vapor, etc. which has heretofore been indispensable for the conventional methods. The rotational or vibrational motion serves to decrease the grain size of crystals of the coating material deposited in a layer on the surfaces under plating. Because of the mutual rubbing the surfaces being plated are smoothened to a surface roughness from 0.4 to 2 microns. The fact that the torque or frequency of vibration is changed in proportion to the progress of plating work permits one to obtain a desired thickness in the deposited layer of the coating material by terminating the plating operation as soon as said change has reached a prescribed level. The plating operation can be automated by using a device adapted so that plating operation is stopped when the torque or frequency which is measured continuously reaches a prescribed level.

What is claimed is:

l. A method for the chemical vapor deposition of fitted surfaces of an article which method comprises, inserting a plunger into a barrel assembly, both plunger and barrel assembly being disposed within a plating chamber, the outer surface of the plunger and the inner surface of the barrel being in fitted relationship to one another, conferring a rotational or vibrational motion upon the plunger or the barrel, supplying vapor of a coating material to the plating chamber, and coating the fitted surfaces of the plunger and barrel during said rotational or vibrational motion.

2. A method according to claim 1, wherein the rate of rotation or the frequency of vibration is measured so that the plating operation is stopped when the measured value reaches a prescribed level. 

1. A METHOD FOR THE CHEMICAL VAPOR DEPOSITION OF FITTED SURFACES OF AN ARTICLE WHICH METHOD COMPRISES, INSERTING A PLUNGER INTO A BARREL ASSEMBLY, BOTH PLUNGER AND BARREL ASSEMBLY BIENG DISPOSED WITHIN A PLATING CHAMBER, THE OUTER SURFACE OF THE PLUNGER AN THE INNER SURFACE OF THE BARREL BEING IN FITTED RELATIONSHIP TO ONE ANOTHER, CONFERRING A ROTATIONAL OR VIBRATIONAL MOTION UPON THE PLUNGER OR THE BARREL, SUPPLYING VAPOR OF A COATING MATERIAL TO THE PLATING CHAMBER, AN COATIN THE FITTED SURFACES OF THE PLUNGER AND BARREL DURING SAID ROTATIONAL OR VIBRATIONAL MOTION.
 2. A method according to claim 1, wherein the rate of rotation oR the frequency of vibration is measured so that the plating operation is stopped when the measured value reaches a prescribed level. 